Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), arrives at her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool

Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), bows to well-wishers as she attends her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool REFILE - CORRECTING DATE

Japan's Princess Aiko, daughter of Emperor Naruhito and Empress Masako, wearing a protective face mask following an outbreak of the coronavirus disease (COVID-19), waves to well-wishers as she attends her graduation ceremony at Gakushuin Girls' Senior High School in Tokyo, Japan March 22, 2020. REUTERS/Issei Kato/Pool REFILE - CORRECTING DATE TPX IMAGES OF THE DAY

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February 22, 2020

Japan's Emperor Naruhito speaks during a news conference on the occasion of his birthday in Tokyo, Japan...

EmperorÊEmeritus Akihito, Emperor Naruhito and Empress Masako wave to well-wishers during a public appearance...

Emperor Emeritus Akihito, Emperor Naruhito and Empress Masako wave to well-wishers during a public appearance for New Year celebrations at the Imperial Palace in Tokyo, Japan, January 2, 2020. REUTERS/Kim Kyung-Hoon

Well-wishers take pictures as Japan's Emperor Naruhito and Empress Masako make a public appearance for...

Well-wishers take pictures as Japan's Emperor Naruhito and Empress Masako make a public appearance for New Year celebrations at the Imperial Palace in Tokyo, Japan, January 2, 2020. REUTERS/Kim Kyung-Hoon

Japan's Empress Emerita Michiko, Emperor Emeritus Akihito, Emperor Naruhito, Empress Masako and royal families attend a public appearance for New Year celebrations at the Imperial Palace in Tokyo, Japan, January 2, 2020. REUTERS/Kim Kyung-Hoon

Japan's Empress Emerita Michiko, Emperor Emeritus Akihito, Emperor Naruhito, Empress Masako and royal families wave to well-wishers during a public appearance for New Year celebrations at the Imperial Palace in Tokyo, Japan, January 2, 2020. REUTERS/Kim Kyung-Hoon

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January 02, 2020

Japan's Emperor Naruhito waves to well-wishers during a public appearance for New Year celebrations at...

Japan's Empress Emerita Michiko, Emperor Emeritus Akihito, Emperor Naruhito, Empress Masako and royal families wave to well-wishers during a public appearance for New Year celebrations at the Imperial Palace in Tokyo, Japan, January 2, 2020. REUTERS/Kim Kyung-Hoon